Highly Z‐Selective Asymmetric Conjugate Addition of Alkynones with Pyrazol‐5‐ones Promoted by N,N′‐Dioxide–Metal Complexes

Wang, Zhen; Chen, Zhenling; Bai, Shuting; Li, Wei; Liu, Xiaohua; Lin, Lili; Feng, Xiaoming

doi:10.1002/anie.201109130

Cited by 109 publications

(17 citation statements)

References 63 publications

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“…Chemie was confirmed by the 1 HNMR and HPLC analyses of its methyl ester (7). Theinherent attribute of N-acyl pyrazole as an acylatinga gent offers an opportunity of readily replacing the pyrazole moiety with various nucleophiles.F or instance, (E)-4aacould be transformed into the ester 8 by displacement with isopropoxide,and to the amide 10 by the coupling with lphenylalanine tert-butyl ester (l-PheOtBu).…”

Section: Methodsmentioning

confidence: 84%

“…[1,2] Accordingly,s tereochemical control involving facial recognition of both the prochiral enolate (enantiocontrol) and the intermediary allenic enolate (olefin geometry control) in this bond-forming process poses an important yet difficult challenge. [6,7] However, most of the existing methods are restricted to reactions with terminal alkynes.O nly af ew successful examples of stereoselective Michael additions to internal alkynes are known to date,a nd they specifically deal with dialkyl acetylene dicarboxylates as the acceptor. [6,7] However, most of the existing methods are restricted to reactions with terminal alkynes.O nly af ew successful examples of stereoselective Michael additions to internal alkynes are known to date,a nd they specifically deal with dialkyl acetylene dicarboxylates as the acceptor.…”

Section: Conjugate Addition Of Enolates (Original Michael Addition)mentioning

confidence: 99%

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ChemInform Abstract: Highly E‐Selective and Enantioselective Michael Addition to Electron‐Deficient Internal Alkynes under Chiral Iminophosphorane Catalysis.

2015

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Ah ighly E-selective and enantioselective conjugate addition of 2-benzyloxythiazol-5(4H)-ones to b-substituted alkynyl N-acyl pyrazoles is achieved under the catalysis of aPspiro chiral iminophosphorane.S imultaneous control of the newly generated central chirality and olefin geometry is possible with aw ide arrayo ft he alkynylM ichael acceptors possessing different aromatic and aliphatic b-substituents,a s well as the various a-amino acid-derived thiazolone nucleophiles.T his protocol provides access to structurally diverse, optically active a-amino acids bearing ageometrically defined trisubstituted olefinic component at the a-position. Conjugate addition of enolates (original Michael addition)to electron-deficient alkynes,s uch as alkynyl carbonyl compounds,o ffers an extremely powerful tool for incorporating av inylic component at the a-position to carbonyl functionalities,thus enabling astraightforward entry to arange of b,gunsaturated carbonyl compounds.[1, 2] Accordingly,s tereochemical control involving facial recognition of both the prochiral enolate (enantiocontrol) and the intermediary allenic enolate (olefin geometry control) in this bond-forming process poses an important yet difficult challenge. [3][4][5] It has been addressed through the development of effective catalytic systems,a nd recent contributions report high levels of both enantioselectivity and E/Z selectivity. [6,7] However, most of the existing methods are restricted to reactions with terminal alkynes.O nly af ew successful examples of stereoselective Michael additions to internal alkynes are known to date,a nd they specifically deal with dialkyl acetylene dicarboxylates as the acceptor.[8] This methodological deficiency highlights the fact that the full potential of this valuable transformation remains to be realized in terms of simultaneous stereocontrol, general applicability,a nd synthetic utility.H erein we disclose the first broadly useful, highly E-selective,and enantioselective conjugate addition of prochiral enolates to b-substituted alkynyl carbonyl compounds under the catalysis of ac hiral iminophosphorane (1; Figure 1). [9][10][11][12][13] Thev ast synthetic potential of this protocol as am eans to access various synthetically relevant carbonyl compounds bearing astereochemically defined, trisubstituted olefinic component at the a-position is demonstrated.In consideration of the unique biological properties of avinylic amino acids, [14,15] 2-benzyloxythiazol-5(4 H)-ones (2), [16,17] N-Cbz amino acid equivalents,w ere selected as the prochiral enolate precursor.Since initial attempts to promote the conjugate addition of the phenylalanine-derived 2a (for structure,s ee Table 1) and methyl 3-phenylpropiolate in the presence of the iminophosphorane 1a did not result in the formation of the desired adduct to any detectable extent, we [a] Reactionswere performed with 0.11 mmol of 2a and 0.1 mmol of 3a in toluene (1.0 mL) in the presence of 1 (10 mol %) at 0 8 8C.[b] Yield of the isolated E/Z mixture.[c] Determined by 1...

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Section: Methodsmentioning

confidence: 84%

Section: Conjugate Addition Of Enolates (Original Michael Addition)mentioning

confidence: 99%

ChemInform Abstract: Highly E‐Selective and Enantioselective Michael Addition to Electron‐Deficient Internal Alkynes under Chiral Iminophosphorane Catalysis.

2015

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“…2011 年, 冯小明小组 [17] 报道了手性 Gd 复合物催化的吡唑酮和偶氮二羧酸酯的不对称加成反应, 以 90%～97%的对映选择性得到了 α-氨基吡唑酮衍 3 , 分别给出了构型相反的产物 [18] . 最近, 该小组报道了手性 Sc 复合物催化的吡唑酮和炔酮的不对称 1,4-加成反应, 以高度的 Z 式选择性和优秀的立体选择性(91%～99% ee) 获得了吡唑酮烯烃衍生物 [19] . 由以上可见, 目前, 吡唑酮作为亲核试剂的不对称合成方法研究主要集中在过渡金属或有机小分子催化的共轭加成, 而对于其它类型的反应研究非常有限.…”

Section: Morita-baylis-hillman (Mbh) 反应是一类重要的 C-c 键形成反应unclassified

Organocatalyzed Asymmetric Allylic Alkylation of MBH-Carbonates with Pyrazolones

Ma¹,

Yuan²,

Wang³

et al. 2014

Acta Chim. Sinica

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The asymmetric allylic alkylation (AAA) reaction is one of the important transformations in asymmetric synthesis, which was intensively studied in the last decade. Recently, the use of Morita-Baylis-Hillman (MBH) carbonates as electrophiles for the AAA reaction has attracted much attention. Pyrazole is an important pharmacophore, which often exhibit various biological and pharmacological activities. In the last years, the asymmetric synthesis using pyrazolones as the nucleophiles were reported by several research groups. However, the work were mainly focused on the asymmetric conjugate addition of pyrazoles to α,β-unsaturated compounds, and other types of enantioselective reactions were seldom studied. Herein, we report the first example of AAA reaction of MBH carbonates using pyrazolones as nucleophiles. In the reaction, we found that different Lewis basic catalyst, namely PPh 3 and DABCO, shown different regioselectivity: PPh 3 gave the γ-selective product whereas DABCO led to a complete β-selectivity. During the catalyst screening, cinchonine gave the best result. The enantioselectivity heavily relied on the choice of solvent: MeOH was superior compared to EtOH, CH 2 Cl 2 , DCE, acetone, CH 3 CN, toluene, m-xylene and PhCl. In the substrate scope study, all the reactions were proceeded smoothly under mild conditions by using cinchonine as the catalyst (20 mol%) and give the β-selective allylic alkylation products with good yields (55%～91%) and high enantioselectivities (up to 93% ee). Based on our experimental results and previous reports, a preliminary mechanism of bifunctional catalysis was proposed. A representative procedure for the asymmetric allylic alkylation of MBH-carbonates with pyrazolones is as follows: to a flask equipped with a magnetic stirring bar was charged with pyrazolone 1 (0.1 mmol) and MBH-carbonate 2 (0.12 mmol) in methanol (2 mL), and then, the cinchonine catalyst (6 mg, 20 mol%) was added under air. The reaction solution was stirred at room temperature for 72 to 96 hours. Then, the mixture was concentrated and purified through a flash chromatography (silica gel, PE/EtOAc, V∶V＝7∶1) to give the corresponding products 3.

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“…[45] In addition, the oxidative destruction of the pyrazolin-5-one ring is also known. [46,47] Among the recent work devoted to the functionalization of pyrazolin-5-ones by the attack of electrophiles [48][49][50][51][52][53][54][55] or radicals [56][57][58] at the 4-position of the heterocycle, only one involved the creation of the CÀN bond, in which azodicarboxylates were used as the nitrogen electrophiles. [52] In this work we proposed aF e(NO 3 ) 3 /NaNO 2 nitrating system that has allowed the synthesis of 4-nitropyrazolin-5-ones bearing as ubstituent at C-4 under ambient conditions (Scheme 1d).…”

Section: Introductionmentioning

confidence: 99%

Mild Nitration of Pyrazolin‐5‐ones by a Combination of Fe(NO₃)₃ and NaNO₂: Discovery of a New Readily Available Class of Fungicides, 4‐Nitropyrazolin‐5‐ones

Krylov

Budnikov

Lopat’eva

et al. 2019

Chemistry A European J

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4‐Nitropyrazolin‐5‐ones have been synthesized by the nitration of pyrazolin‐5‐ones at room temperature by employing the Fe(NO3)3/NaNO2 system. The method demonstrated selectivity towards the 4‐position of pyrazolin‐5‐ones even in the presence of NPh and allyl substituents, which are sensitive to nitration. It was shown that other systems containing FeIII and nitrites, namely Fe(NO3)3/tBuONO, Fe(ClO4)3/NaNO2, and Fe(ClO4)3/tBuONO, were also effective. Presumably, FeIII oxidizes the nitrite (NaNO2 or tBuONO) to form the NO2 free radical, which serves as the nitrating agent for pyrazolin‐5‐ones. The synthesized 4‐nitropyrazolin‐5‐ones were discovered to be a new class of fungicides. Their in vitro activities against phytopathogenic fungi were found comparable or even superior to those of commercial fungicides (fluconazole, clotrimazole, triadimefon, and kresoxim‐methyl). These results represent a promising starting point for the development of a new type of plant protection agents that can be easily synthesized from widely available reagents.

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Highly Z‐Selective Asymmetric Conjugate Addition of Alkynones with Pyrazol‐5‐ones Promoted by N,N′‐Dioxide–Metal Complexes

Cited by 109 publications

References 63 publications

ChemInform Abstract: Highly E‐Selective and Enantioselective Michael Addition to Electron‐Deficient Internal Alkynes under Chiral Iminophosphorane Catalysis.

ChemInform Abstract: Highly E‐Selective and Enantioselective Michael Addition to Electron‐Deficient Internal Alkynes under Chiral Iminophosphorane Catalysis.

Organocatalyzed Asymmetric Allylic Alkylation of MBH-Carbonates with Pyrazolones

Mild Nitration of Pyrazolin‐5‐ones by a Combination of Fe(NO₃)₃ and NaNO₂: Discovery of a New Readily Available Class of Fungicides, 4‐Nitropyrazolin‐5‐ones

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Highly Z‐Selective Asymmetric Conjugate Addition of Alkynones with Pyrazol‐5‐ones Promoted by N,N′‐Dioxide–Metal Complexes

Cited by 109 publications

References 63 publications

ChemInform Abstract: Highly E‐Selective and Enantioselective Michael Addition to Electron‐Deficient Internal Alkynes under Chiral Iminophosphorane Catalysis.

ChemInform Abstract: Highly E‐Selective and Enantioselective Michael Addition to Electron‐Deficient Internal Alkynes under Chiral Iminophosphorane Catalysis.

Organocatalyzed Asymmetric Allylic Alkylation of MBH-Carbonates with Pyrazolones

Mild Nitration of Pyrazolin‐5‐ones by a Combination of Fe(NO3)3 and NaNO2: Discovery of a New Readily Available Class of Fungicides, 4‐Nitropyrazolin‐5‐ones

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Mild Nitration of Pyrazolin‐5‐ones by a Combination of Fe(NO₃)₃ and NaNO₂: Discovery of a New Readily Available Class of Fungicides, 4‐Nitropyrazolin‐5‐ones